The present invention relates generally to the field of telecommunications and, in particular, to transport of control data over a ring network such as the transport of signals between a set top box and a master controller at a head end of a cable system. Further applications include, for example, monitoring and controlling power consumption of subscribers of a power company and network management of a cable television or other distributed system.
Telecommunications companies, such as cable television operators, provide xe2x80x9cprogrammingxe2x80x9d or xe2x80x9ccontentxe2x80x9d to subscribers over a wide variety of networks. Initially, cable operators provided subscribers with improved access to a number of commercial and premium programming stations over a network of coaxial cables. Further, new commercial programming stations have entered the marketplace over the cable networks. These stations include the USA Network, Nickelodeon, CNN, and others.
To further increase revenues, some cable operators further provide access to selected movies and other programming on a pay-per-view basis. Conventionally, the cable operators schedule a number of showings of specified movies on selected channels and at specified times. Typically, these systems operate by scrambling the video portion of the pay per view channel. When a subscriber requests the program, the cable operator activates the descrambler at the subscriber""s premises to descramble the selected show at the scheduled time.
With the increase in competition for the entertainment resources of consumers, cable operators and other content providers have tried to create more flexible systems for delivering video programming to subscribers. For example, the cable industry has begun to design networks that provide xe2x80x9cvideo on demand.xe2x80x9d Essentially, with this type of system, a user can select from a list of movies for viewing at any time. One problem with delivering video on demand, and even more traditional pay per view, is transmitting the request for the programming from the subscriber to the head end controller of the cable network.
In conventional systems, a set top box can be used to transmit a request for a pay per view event to the head end of the cable system. A subscriber enters information, such as a program code, into the set top box via either a key pad on the box or a remote control. This information is typically transmitted over the coaxial cable to a hub of the cable network as a low speed, e.g., 13800 baud, digital signal. At the hub, the signal is received by Set Top Box Controller (STBC). The STBC converts the signal to Ethernet packets which are transmitted around the network to a master controller. If the network interconnection is a SONET, leased line, or other standard telecommunications network interconnection, the Ethernet packets typically must be encapsulated or transformed into another format for transmission over that backbone to the head end controller to complete the set up of the pay per view event for the subscriber. Set top boxes, and controllers with Ethernet interfaces are commercially available from companies such as the ANIC set top box controller product from General Instruments Corporation.
In a further effort to increase revenues and profits from their investment, operators are considering, or planning to add new services that can be carried over their systems. Among the many services that cable operators are considering, or planning to offer are meter reading for utilities, energy consumption control for utilities, and other services, all of which can be carried over the same network infrastructure that carries the control data from a set top box and a set top box controller.
Additionally, in an effort to cut costs, cable operators are installing more and more remote control and management devices for controlling and managing elements of their own network. These devices often have Ethernet interfaces for the information that must be transferred from the primary site with the master controller or control console, to the control devices distributed throughout the network. The data that must be transferred among these devices can also be transferred over the same infrastructure that would carry set top box and utility control information.
Conventionally, Synchronized Optical Networks (SONET) rings provide a high capacity backbone to interconnect the various hubs of a cable network. SONET rings were developed around the ability to transport voice channels with fixed size packets in a high speed ring network for telephony service. SONET rings are expensive to use to carry information from an STBC or other controller to a head end controller due in part to the fact that the Ethernet packets usually are converted to a different format, e.g., asynchronous transfer mode (ATM).
As an alternative to using the SONET rings to transport the data to the head end, some cable companies lease telephone lines for connecting the various STBCs and other controllers to the head end controller. This is an expensive solution to get the data to the head end.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a transport mechanism to carry control data in a telecommunications network.
The above-mentioned problems with telecommunications systems and other problems are addressed by the present invention and will be understood by reading and studying the following specification. A telecommunications network is described which uses a ring of ring switches to provide a backbone transport mechanism for data packets that is transparent to the data and protocols contained in the data packets. The ring switches can include a number of different features, alone or in combination, to implement this backbone network. Ring switches with such features are described in detail in U.S. Pat. No. 6,154,462, entitled Circuits and Methods for a Ring Network, issued on Nov. 28, 2000, and in Section III below. The ring switches include, but are not limited to, the following:
1. A ring switch in which packets are switched on to a unidirectional ring based on comparing a destination identifier, which may already be in the packet, to a table in the ring switch.
2. A ring switch in which packets are switched off and removed from the unidirectional ring based on comparing a destination identifier, which may already be in the packet, to a table in the ring switch thus freeing bandwidth for use by other devices and switches on the ring.
3. A ring switch in which packets received from a unidirectional ring, are placed back on the unidirectional ring based on comparing a destination identifier, which may already be in the packet, to a table in the ring switch.
4. A ring switch in which packets which have traveled completely around the ring are terminated by comparing a source identifier which may be already in the packet to a table, a switch identifier that was added by the ring switch to a table, or a hop counter that has reached a threshold value.
5. A ring switch in which no modification is made to the original packet in order to cause the packet to transmit from the local ports of one ring switch, around the ring to the local ports of another ring switch because the destination identifiers used to compare to the table are already contained in the original packet.
6. A ring switch in which no modification is made to the original packet in order to cause the packet to be terminated when the packet has traveled completely around the ring because the source identifiers used to compare to the table are already contained in the original packet.
7. A ring switch in which the tables are built automatically (self learned) by virtue of reading the source identifiers of each packet received by the ring switch.
8. A ring switch in which the original packet is modified slightly by the ring switch when placing the packet on a unidirectional ring by the addition of a switch identifier such that when the packet has traveled completely around the ring and back to the originating ring switch, the packet is terminated by detecting its own switch identifier.
9. A ring switch in which the original packet is modified slightly by the ring switch when placing the packet on the unidirectional ring by the addition of a counter, such that when the packet passes through each ring switch, the counter is incremented (or decremented) and the packet is terminated by any switch when the counter reaches a selected value.
This transport mechanism is simple and low cost to implement. Such networks can carry, for example, control data between a head end and hubs of a cable network to set up and deliver pay per view, video on demand or near video on demand programming. The network can also be used, in other embodiments, to provide remote access to utility meters, to centralize network management of the cable network, and other appropriate monitoring and control functions.